Make HDR code build on systems where patched Qt is not available
You need to add -DHAVE_HDR to enable HDR-related code. But
you will need a patched Qt for that.
The patch also makes the code behave correctly on Linux
The patch also makes it possible to select OpenGL ES renderer
on Linux. The renderer is selected fine, but doesn't work for
some reason. I guess some texture format is set incorrectly.